Toothbrushes are of the following types: a commonly used toothbrush, which has a handle portion and a brush portion formed integrally so as to be manually operated; and, an electric toothbrush housing an electrically operated motor which is driven by a current flowing from a dry battery or a receptacle.
Tooth-brushing methods using toothbrushes include a bath process, a rolling process, a forns process, a scrapping process, and the like. In accordance with the bath process, bristles on the brush portion are driven in short and quick movements, while being held in contact with the teeth and the gums at about a 45.degree. angle. In the rolling process, the handle portion of the toothbrush is pivoted about an axial direction of the handle portion with a flick of the wrist, thereby causing the brush portion to be pivoted in synchronism therewith. In the forns process, while the toothbrush is held against the teeth at a right angle, the bristles on the brush portion are forced into movement such as to draw a circle. In the scrapping process, while tips of the bristles on the brush portion of the toothbrush are held in contact with the teeth at a right angle, the bristles on the brush portion are driven in short and quick movements.
Although the tooth-brushing methods vary from user to user depending on such factors as the tooth rows and brushing habits of the user as well as the types or extent of periodontal ailments, the methods can broadly be classified into the above four categories.
In some schools, the dental profession educates pupils about brushing of the teeth as a part of educational programs. This system teaches them proper tooth-brushing methods in order to provide dental hygiene management or cure in accordance with states of the teeth.
The electric toothbrush has been developed so as to require less time for brushing the teeth and to afford improved convenience of use, compared with the manually operated toothbrush.
Further, in the electric toothbrush, there is one type in which a revolving force imparted from an electrically operated motor housed therein is converted into, for example, a rolling or otherwise sliding motion by a revolving force-converting mechanism. As another type of electric toothbrush, there is a vibrating toothbrush in which an eccentric heavy weight is attached to the electrically operated motor. These electric toothbrushes are designed to massage the gums as well as brushing tooth surfaces, with the brush portion being held against the teeth, thereby serving as a hygienic instrument for protecting the teeth and the gums from any ailments.
Moreover, the electric toothbrush is usually constructed to allow the brush portion to be removed with respect to the handle portion, so that the brush portion is replaceable when deformations and the like of the bristles on the brush portion over many years of use detract from the ability of the bristles.
In view of conventional manual-operated toothbrushes, different brushing methods can be practiced using a single toothbrush according to the different manner in which the toothbrush is held or moved. However, the action of brushing the teeth must be sustained more than 20 minutes in accordance with a proper tooth-cleaning process in order to secure sufficient cleaning effectiveness. This is inconvenient for brushing because of such a considerable period of time.
Meanwhile, electric toothbrushes are constructed to require less time for brushing than the manually operated toothbrushes, in consideration of respective movements dictated by, for example, the rolling process and/or the bath process, to be specific, one of the movement by the rolling process and the movement by the bath process, or otherwise a changeover between the former and the latter.
In conventional types of vibrating electric toothbrushes, a vibration frequency has usually been established within a limit of about 2,000 to about 3,000 rpm. However, inconveniences arise because the vibration ranging from about 2,000 and about 3,000 rpm produces a feeling of less comfort during brushing, as shown in FIG. 6. This is disadvantageous in practical use, and only insufficient cleaning effectiveness can be obtained.
Another inconvenience arises when the vibration frequency of the electric toothbrush is set at a prescribed value, for example, more than 8,000 rpm. That is, although this setting ensures sufficient cleaning effectiveness, a curve indicative of comfort, as shown in FIG. 6, will be advanced from a region of comfort to a region of discomfort. This is disadvantageous in practical use because of a consequential increase in an uncomfortable feeling during brushing.
In order to eliminate the above-described disadvantages, there is provided a tooth-brushing method according to the present invention by means of an electric toothbrush including a handle portion, an electrically operated motor built in the handle portion, a brush portion held in engagement with the handle portion, and a heavy eccentric mass designed to produce vibration upon actuation of the motor, wherein the motor is actuated to bring the brush portion into vibration so that brushing is practiced through the aid of the vibration, the tooth-brushing method comprising the steps of: predetermining respective weights of the electric toothbrush and the eccentric heavy mass as well as an eccentric location of the center of gravity of the eccentric heavy mass; establishing and output of the motor within a range of about 6,000 to about 8,000 rpm in accordance with the predetermined conditions; producing a vibration ranging from about 6,000 to about 8,000 rpm by actuating the motor; conducting the vibration to tips of bristles on the brush portion, and increasing a pressing force acting along an axial direction of the bristles by the use of a minute circular motion which is produced by the vibration in a plane perpendicular to an axial direction of the brush portion; and brushing the teeth by utilizing the increased pressing force.
In accordance with the present invention as described above, tooth brushing is practiced by means of the electric toothbrush which is constructed to produce a vibration within the range of about 6,000 to about 8,000 rpm. To this end, the vibration in the above range produced by the actuation of the electrically operated motor is conducted to the tips of the bristles on the brush portion. A pressing force acting along the axial direction of the bristles is increased by the minute circular motion which is produced by the vibration in the plane perpendicular to the axial direction of the brush portion. This process ensures a high level of comfort and sufficient tooth-cleaning effectiveness as a result of the above vibration frequency.